1. Field of the Invention
The present invention relates to a linear compressor, and in particular to an oil circulation structure for a linear compressor and a method of the same which are capable of increasing a cooling effect by supplying an oil to a cylinder and exhaust portion and implementing an excellent lubrication performance at a friction portion for thereby enhancing an efficiency of a compressor and increasing a reliability of the product.
2. Description of the Background Art
A high efficiency and power conserving feature is a new trend in a home appliance such as a refrigerator, an air conditioner, etc. The technology for a compressor which forms a freezing cycle apparatus for a refrigerator, an air conditioner, etc. has been intensively developed.
As shown in FIG. 1, the construction of a conventional linear compressor will be explained.
FIG. 1 is a vertical cross-sectional view illustrating an example of a conventional linear compressor. The linear compressor includes a compressor unit 90 horizontally installed in the interior of a hermetic container 1 for sucking, compressing and exhausting a refrigerant gas, and an oil supply unit 10 installed at a lower portion of the compressor unit 90 for supplying an oil at the inner lower surface into the interior of the compressor unit 90.
The compressor unit 90 includes a hollow cylindrical frame 20, a hollow cylindrical cylinder 30 engaged to a portion of the frame 20, an outer lamination 40 and a coil assembly 40a engaged to an inner surface of the frame 20, an inner lamination 50 engaged to an outer portion of the cylinder at a certain interval from the outer lamination 40, a piston(70) integrally formed with a rotator 60 which linearly reciprocates between the outer lamination 40 and the inner lamination 50 and installed in the interior of the cylinder 20, a hallow cylindrical cover 80 engaged at the other end of the frame 20, and a valve cover 3 including a valve assembly 2 therein for covering an end portion of the cylinder 30.
The structure that an oil is supplied to the compressor unit 90 by the oil supply unit 10 and is exhausted therefrom will be explained with reference to FIG. 2.
First, an oil supply pocket 31a is formed at a lower portion contacting with the frame 20 and the cylinder 30 and communicates with an oil suction path 11 through which an oil is sucked from the oil supply unit 10. An oil exhaust pocket 31b is formed at an upper portion and communicates with an oil exhaust hole(not shown) formed to exhaust the oil in the direction of one side of the frame 20.
In addition, oil paths 32a and 32b are formed at a certain inclination angle to flow an oil up to the inner surface of the cylinder 30 via the oil supply and exhaust pockets 31a and 31b, namely, up to the contact portions of the cylinder 30 and the piston 70. An oil pocket 75 is formed at the inner ends of the oil paths 32a and 32b, namely, at the friction portion of the piston 70 and the cylinder 30. The oil pocket 75 of the friction portion is formed on an outer surface of the piston 70 and has a certain width and groove over the entire surfaces.
In the drawings, reference numeral 4 represents a refrigerant suction tube, 24 and 25 represent coil springs elastically supported between the cylinder 30 and the piston 70, and the piston 70 and the cover 80.
The oil circulation operation of the conventional linear compressor having an oil circulation structure will be explained.
When a power is applied to the compressor unit 90, the rotator 60 reciprocates between the outer lamination 49 and the inner lamination 50. Therefore, the piston 70 reciprocates in the cylinder 30. The refrigerant gas flown into the hermetic container 1 is sucked into a compression chamber of the cylinder 30 via the refrigerant flow path formed at a center portion of the piston 70 and is compressed therein, and then is exhausted via the exhaust valve assembly 2 and the exhaust cover 3. The above-described operation is repeatedly performed.
In the oil supply and exhaust process in which the operation of the compressor unit 90 is performed, the oil supply unit 10 is vibrated together with the compressor unit 90 and suck an oil. The thusly sucked oil is pumped along the oil suction path 11 and is flown into the friction portion oil pocket 75 via the oil supply pocket 31a and the oil introduction oil path 32a. The thusly introduced oil lubricates and cools the friction portion between the cylinder 30 and the piston 70 and is exhausted to the outside of the compressor unit 90 sequentially via the oil exhaust path 32b, the oil exhaust pocket 31b and the oil exhaust hole(not shown).
In other words, as shown in FIG. 3, in the conventional oil circulation process, the oil supply unit 10 performs an oil pumping step for pumping an oil from the inner bottom surface of the hermetic container 1, and in the friction portion oil supply step, the thusly pumped oil lubricates and cools the friction portion between the cylinder 30 and the piston 70. In addition, an oil returning step, the oil passed through the friction portion oil supply step returns to the inner bottom surface of the hermetic container 1 via an oil exhaust hole(not shown) of the frame 20.
In the thusly constituted conventional linear compressor having the oil circulation structure, the oil supplied from the oil supply unit 10 flows through the introduction oil path 32a of the cylinder 30 and is introduced into the friction portion of the cylinder 30 and the piston 70. After a certain lubricating process therein, the oil is flown via the exhaust oil path 32b of the cylinder 30 and is exhausted to the outside of the compressor unit 90. Therefore, the oil lubricates the friction portion of the cylinder 30 and the piston 70 and cools the piston 70.
However, in the conventional oil circulation structure for a conventional linear compressor, the exhaust valve assembly and valve cover which are heated by an exhaust gas are not effectively cooled. In addition, an effective cooling operation is not performed with respect to the cylinder, so that a re-expansion loss occurs due to the heating of the suction gas for thereby decreasing the efficiency of the compressor.